Fibre Channel (SAN)

Reply
Contributor
Posts: 66
Registered: ‎03-31-2013

Link Timeout

Dear All

10.66.12.173S0,P-1(23): Link Timeout on internal port  ftx=-1367794193 tov=2000 (>1000) vc_no=1 crd(s)lost=5 complete_loss:1.

From the above msg i would unserstand that there is reset on VC 1,

but is it due to BB credits exhaustion LR is issued.

Is the only way to avoid it is to increase BB credits

If anything else can cause this, someone anyone help me

Valued Contributor
Posts: 761
Registered: ‎06-11-2010

Re: Link Timeout

Hi,

That event reports a link timeout in the a backend port of the switch, it has nothing to do with the BB credits in the front end ports.

What FOS version is the switch running? with v6.4.2a you can enable a feature of bottleneck monitor that reviews this kind of events, and when a credit loss situation is detected it resets the internal link

Please, activate the following (it is non-disruptive):

bottleneckmon --enable –alert

bottleneckmon --cfgcredittools -intport -recover onLrOnly


this may fix the issue, but if it does not, you'll have to powercycle the switch. And if the powercycle does not help either, you should think in replacing the switch (or learn to live with it...   )



Kind regards,

Felipon


Contributor
Posts: 66
Registered: ‎03-31-2013

Re: Link Timeout

Can you pls tell me what does credit loss mean ?

Valued Contributor
Posts: 761
Registered: ‎06-11-2010

Re: Link Timeout

the flow control mechanism implemented in Fibre Channel is based in Buffer-to-buffer Credits. If one of these credits is lost (for example for a frame corruption) in the backend of the switch -as it seems to be the case- it reports this event.

Contributor
Posts: 66
Registered: ‎03-31-2013

Re: Link Timeout

Thanks, Why VC is coming into picture can you pls explain the same

Valued Contributor
Posts: 761
Registered: ‎06-11-2010

Re: Link Timeout

Virtual Channels are also used in the backend connectivity and each VC is asssigned a certain number of BB credits.

Contributor
Posts: 66
Registered: ‎03-31-2013

Re: Link Timeout

Thank you, So is there any thing to do with BB credits  or no

Valued Contributor
Posts: 761
Registered: ‎06-11-2010

Re: Link Timeout

yes, it has to do with BB credits. that event reports the loss of a BB credit assigned to VC1

Rgds

Contributor
Posts: 66
Registered: ‎03-31-2013

Re: Link Timeout

Hello

bottleneckmon --cfgcredittools -intport -recover onLrOnly


How this command helps me can you pls let me know, how does this handle the situation.

If LR is issued will it not display msg "S0,P-1(23): Link Timeout on internal port  ftx=-1367794193 tov=2000 (>1000) vc_no=1 crd(s)lost=5 complete_loss:1"

Valued Contributor
Posts: 761
Registered: ‎06-11-2010

Re: Link Timeout

Hi,

When a BB credit is lost, the only way to recover it is to reset the port. Previously, before this command was developped the switch had to be rebooted (or theport blade, depending on the switch model); now, this command resets only the backend port where the lost BB credit was detected.

Rgds

Join the Community

Get quick and easy access to valuable resource designed to help you manage your Brocade Network.

vADC is now Pulse Secure
Download FREE NVMe eBook